Reactions of Group 8 Transition-Metal Ions (Fe+, Co+, and Ni+) with Cyclic Hydrocarbons in the Gas Phase

Article abstract of DOI:10.1021/ja00364a003

The gas phase reactions of group 8 transition metal ions (Fe⁺, Co⁺, and Ni⁺) with cyclic hydrocarbons were studied by Fourier transform mass spectrometry.Product structures were probed by using collision-induced dissociation (CID) and H/D exchanges.All three metal ions react with cyclobutane to generate ring-cleavage products exclusively.This is in contrast to reactions with cyclopropane and cyclohexane, where dehydrogenation dominates, producing cycloalkene- and cycloalkadiene-metal ion complexes.Bis(ethene)-metal ion complexes, formed in secondary reactions, are shown not to be in equilibrium with metallacyclopentanes.Metallacyclopentanes decompose by symmetric ring cleavage, producing an ethene-metal ion complex, or by an initial 1,3-hydrogen shift, producing a linear butene complex which dehydrogenates, forming a butadiene-metal ion complex.Both Fe-c-C5H6⁺ and Co-c-C5H6⁺ undergo six H/D exchanges with D2.The rate constant for the first exchange is found to be about an order of magnitude faster than for the second exchange.Cycloalkadiene products of Fe⁺ and Co⁺ react rapidly with their corresponding cyclic-alkane analogues exclusively by multiple dehydrogenations.Cycloalkadiene products of Ni⁺, however, were found to be unreactive with cyclic alkanes.